Java Programming Network Programming TCP Programming

Complete the development of TCP programs using Socket s

Use this class to easily establish a reliable, two-way, continuous, point-to-point communication connection

In Socket development, the server side uses ServerSocket to wait for the client to connect. For Java network programs, each client uses a Socket object to represent

ServerSocket Class and Socket Class

The ServerSocket class is primarily used for server-side program development to receive connection requests from clients

ServerSocket class

Method	Effect
public ServerSocket(int port) throws IOException	Create a ServerSocket instance and specify a listening port
public Socket accept() throws IOException	Waiting for client connection, blocking until connection
public InetAddress getInetAddress()	Return the IP address of the server
public boolean isClosed()	Returns the closed state of the ServerSocket
public void close() throws IOException	Close ServerSocket

Use the accept() method to wait for client connections each time the server runs

The server side will be blocked after this method is executed

The program cannot continue down until the client is connected

The return value type of this method is Socket

Each Socket represents a client object

Socket class

Method	Effect
public Socket(String host,int port) throws UnknownHostException,IOException	Construct the Socket object, specifying the host name and port to connect to the server
public InputStream getInputStream() throws IOException	Returns the input stream for this socket
public OutputStream getOutputStream() throws IOException	Returns the output stream of this socket
public void close() throws IOException	Close this Socket
public boolean isClosed()	Determine if this socket is closed

On the client side, the program can get the output information of the server through the getInputStream() method of the Socket class, and on the server side, it can get the output information of the client through the getOutputStream() method.

Write TCP program

Write server program

import java.io.IOException;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Hello {
    public static void main(String[] args) throws IOException {
        ServerSocket server = null;
        Socket client = null;
        PrintStream out = null;
        server = new ServerSocket(8889);
        System.out.println("Server running, waiting for client connection");
        client = server.accept();
        String str = "HELLO";
        out = new PrintStream(client.getOutputStream());
        out.println(str);
        out.close();
        client.close();
        server.close();
    }
}

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Write client program

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.Socket;

public class Hello2 {
    public static void main(String[] args) throws Exception{
        Socket client = null;
        client = new Socket("localhost",8889);
        BufferedReader buf = null;
        buf = new BufferedReader(new InputStreamReader(client.getInputStream()));
        String str = buf.readLine();
        System.out.println("Server Output:"+str);
        client.close();
        buf.close();
    }
}